SSBII3

 

QCM-D Applications in Biomaterials

Alan A. Brain
Smith & Nephew Group Research Centre
York.

Quartz crystal microbalances have long been used as coating thickness monitors in vacuum systems. Since it has been demonstrated that the QCM can be used in the liquid phase there has been a resurgence of interest in this technique. The resonant frequency of the crystal is dependent on the total oscillating mass including water coupled to the oscillation. Thin films attached to the crystal decrease the resonant frequency, if the layer is rigid the mass can be calculated using the Saurbrey equation.

C = mass constant of the system n = 1,3,5,7 is the overtone number

Films that are not rigid do not fully couple to the crystals oscillations and the resonance is damped. By measuring the dissipation of the resonance it is possible to measure viscoelastic properties of the adlayer, hence the QCM becomes QCM-D where D is dissipation.

The system is an extremely sensitive balance capable of detecting mass changes of the order of a nanogram.

The QCM-D is being applied to a wide variety of applications. Initially the development was driven as a tool to measure protein binding. In our laboratories we are using the QCM-D to study protein – protein interactions, gel formation in fibrin systems and the degradation of polymers such as lactides and glycolides.